Tungsten disulfide thin film/p-type Si heterojunction photocathode for efficient photochemical hydrogen production
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Research Letter
Tungsten disulfide thin film/p-type Si heterojunction photocathode for efficient photochemical hydrogen production Ki Chang Kwon†, Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea; School of Chemical Engineering and Materials Science, Chung-Ang University, Seoul 06974, Republic of Korea Seokhoon Choi†, Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea Kootak Hong, Dinsefa Mensur Andoshe, Jun Min Suh, and Changyeon Kim, Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea Kyoung Soon Choi, Advanced Nano Surface Research Group, Korea Basic Science Institute, Daejeon 34133, Republic of Korea Jeong Hyeon Oh, and Soo Young Kim, School of Chemical Engineering and Materials Science, Chung-Ang University, Seoul 06974, Republic of Korea Ho Won Jang, Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea Address all correspondence to Soo Young Kim, Ho Won Jang at [email protected], [email protected] (Received 22 January 2017; accepted 24 May 2017)
Abstract We demonstrate the tungsten disulfide (WS2) thin film catalysts prepared by the sulfurization of vacuum deposited WO3 thin films for efficient hydrogen production with over 90% Faradaic efficiency. The 23-nm-thick WS2 thin film catalyst heterojunction with p-type silicon photocathode could exhibit a photocurrent density of 8.3 mA/cm2 at 0 V versus a reversible hydrogen electrode (RHE), a low onset potential of 0.2 V versus RHE when photocurrent density reaches −1 mA/cm2 and long-term stability over 10 h. The enhanced catalytic activities of WS2/p-Si photocathodes compared with the bare p-Si photocathode originate from a number of edge sites in the synthesized polycrystalline thin films, which could act as hydrogen evolution catalyst.
Introduction Energy conversion directly from solar energy to chemical bonds is one of the most attractive ways to overcome the global energy crisis.[1–3] Recently, hydrogen (H2) has received tremendous attention as an alternative to fossil fuels owing to its sustainability and minimal environmental impact. In this situation, the photoelectrochemical (PEC) water splitting is a promising approach for the sustainable production of hydrogen as a fuel from the sunlight. Among the various candidate semiconductors for PEC water splitting, p-type silicon ( p-Si), which has a narrow bandgap of 1.1 eV can absorb wide range of wavelengths ranging from ultraviolet to near infrared.[4,5] It also has costefficiency and well-organized photovoltaic technologies. However, the p-Si has high overpotential at the interface of p-Si/electrolyte because of its poor hydrogen evolution reaction (HER) kinetics originating from the high hydrogen adsorption of Gibbs free energy.
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